Joined multiple cam comprising individual prefabricated cams

ABSTRACT

A joined prefabricated individual cam ( 1, 2 ), comprising multiple cams for an adjustable camshaft in particular for an internal combustion engine of a motor vehicle, whereby the camshaft has two shafts mounted concentrically one inside the other, namely an inner shaft and an outer shaft, and the joined multiple cam is fixedly pinned to the inner shaft via radial openings provided in the outer shaft with a rotatable bearing on the outer shaft, should be easy and inexpensive to manufacture.  
     To this end, such a multiple cam is characterized in that at least one prefabricated individual cam ( 1, 2 ) is placed as a cam ring on the outside circumference of a carrier pipe ( 3 ″) at an axial distance from the neighboring individual cams ( 1, 2 ) and is fixedly connected to this carrier pipe ( 3 ″) at a predetermined angle of rotation and axial distance assignment.

The invention relates to a joined multiple cam consisting individual prefabricated cams for an adjustable camshaft in particular according to the preamble of Patent claim 1.

Joined multiple cams are known from DE 10 2004 009 074 B3. Manufacturing of these cams is complicated.

The invention relates to the problem of designing multiple cams composed of individual cams so they can be manufactured more easily, in particular with respect to multiple cams for adjustable camshafts. These adjustable camshafts are those which consist of two shafts mounted concentrically one inside the other, namely an inner shaft and an outer shaft whereby a generic multiple cam is mounted rotatably on the outer shaft and is rigidly pinned to the inner shaft via a radial opening in the outer shaft.

This object is achieved with a generic multiple cam through a design according to the characterizing feature of Patent claim 1.

Advantageous and expedient embodiments are the subject matter of these subclaims.

In particular in the case of multiple cams for an adjustable camshaft in which the multiple cams are pinned to an inner shaft in the manner described above, the present invention offers the advantage of being able to perform the pinning exclusively within an area of the carrier pipe. In such an embodiment, the material of the camshafts, which is designed for high stresses, may be limited to these elements, whereas the areas of the multiple cam which serve on the one hand as spacers between the individual cams and on the other hand as abutments for the pinning may be made of another material, in particular a material that can be made available less expensively.

A number of alternative embodiments of the invention are depicted in the drawing.

The diagrams in these drawings show:

FIGS. 1 through 10: each shows different embodiment in a longitudinal section, a front view and a perspective view of a multiple cam.

In all embodiments, the respective multiple cam comprises two individual cams, namely a first individual cam 1 and a second individual cam 2, which are joined together in different axial positions with a fixed rotational angle via a carrier pipe 3. In the following description of the individual embodiments, each of which will be allocated to the diagram in one of the figures, reference will be made to these elements using the same reference numerals. If these elements are different in design, these different embodiments will each be characterized with different indices while otherwise using the same reference numeral.

All the multiple cams illustrated in the drawing and described below are intended primarily for an adjustable camshaft (not shown in the drawing) in which they are mounted on an outer shaft and are fixedly pinned to an inner shaft situated coaxially inside this outer shaft. The areas in which the shaft is pinned via a pin 4, shown here as an example only in individual exemplary embodiments, are situated between the individual cams 1, 2 in an area of a carrier pipe 3.

DESCRIPTION OF THE INDIVIDUAL EMBODIMENTS WITH CORRELATION TO THE RESPECTIVE FIGURE

FIG. 1

Two individual cams 1, 2 are joined together by a carrier pipe 3. At the axial center of this carrier pipe 3 there is a ring collar 5 protruding axially outward. A individual cam 1, 2 is placed on the end areas of the carrier pipe 3 which have a smaller diameter and each of which has a circular outside, and the individual cam is fixedly connected to the carrier pipe 3 by a press fit. The press fit may be reinforced by an adhesive bond between the individual cams 1, 2 and the carrier pipe 3. The axial distance between the individual cams 1, 2 is determined by the ring collar 5. As in all the embodiments described below, after finishing machining the individual cams 1, 2 may be mounted on the carrier pipe 3 with predetermined angles of rotation so that such a multiple cam can be placed on the outer shaft of an adjustable camshaft in a finished machine form and then in the ideal case need not be reworked anymore. Different materials may be used for the individual cams 1, 2 on the one hand and the carrier pipe 3 on the other hand. The individual cams 1, 2 may also be made of different materials if different operating stresses act on the camshaft for these individual cams 1, 2.

For mounting such a multiple cam, which is mounted on the outer shaft in the case of an adjustable camshaft, the multiple cam may be pinned to the inner shaft radially through the area of the ring collar 5. Such a type of pinning is illustrated in FIG. 8 in particular.

FIG. 2

This embodiment differs from that according to FIG. 1 essentially in that the carrier pipe 3′ does not have an outer ring collar 5. In addition it should be pointed out in particular with respect to this exemplary embodiment that the mounting of the individual cams 1, 2 on the carrier pipe 3, 3′ or all the other carrier pipe embodiments described below in any desired type of connection may consist of the possibilities with which those skilled in the art are familiar. Alternately or cumulatively, the individual cams 1, 2 may be connected to the carrier pipe in a press fit by welding, soldering, gluing and/or by a form-fitting connection.

FIG. 3

In this embodiment, a carrier pipe 3″ is used, its outer ring collar 5′ being shaped out of the carrier pipe 3 by molding the carrier pipe 3″ in a high-pressure internal molding process, for example. In the area of the ring collar 5′, the carrier pipe 31 has an inside circumferential area where the diameter is widened. In the case when such a multiple cam is pinned to the outer shaft of a camshaft, such a widened inside diameter area has the advantage that when joining the multiple cam on the outer shaft of an adjustable camshaft, a manufacturing-related burr on the inside circumference of the ring collar 5 cannot have an interfering effect on the radial bore in the ring collar 5′ through which the pinning may be accomplished. Because of the advantage of an inside circumferential area of a ring collar 5 having a widened diameter, as mentioned last, such a carrier pipe design may also be provided by machining a carrier pipe 3 out of solid material.

FIG. 4

In this embodiment, a carrier pipe 3′″ does not pass through the internal circumferential areas of the individual cams 1, 2. This carrier pipe 3′″ is instead mounted essentially only axially between the individual cams 1, 2. In the individual cams 1, 2 ring grooves 6 that are open toward the inside radially are provided on the inside edge of each adjacent end face. In the area of these ring grooves 6, the individual cams 1, 2 each extend beyond the carrier pipe 3′″ in the respective areas of the ring grooves 6. The connection between the individual cams 1, 2 and the carrier pipe 3′″ may be established in the usual way alternatively or cumulatively by welding, soldering, gluing or providing a press fit.

FIG. 5

The carrier pipe 3 ^(IV) used here is one which is provided with a ring flange 7 protruding radially outward on one axial end. A spacer ring 8, also placed on the carrier pipe 3 ^(IV), serves to maintain the space between the two individual cams 1, 2 placed on this carrier pipe. On the end of carrier pipe 3 ^(IV) opposite the ring flange 7, a pin may be inserted through radial bores provided there in the carrier pipe 3 ^(IV). The bores for the pin 4 may be arranged in the axial direction of carrier pipe 3 ^(IV) in such a way that they engage in the area of an adjacent first individual cam 1, 2. In this case, the respective individual cam 1, 2 is provided with grooves 9 which run radially and are assigned to the bore for the pin 4. The engagement of the pin 4 in these radial grooves 9 yields a twist-proof form-fitting connection between pin 4 and the adjacent individual cams. Axial bracing of the individual cams 1, 2, including the spacer ring 8, may also be achieved through the pin 4 by means of a corresponding orientation in the axial direction of carrier pipe 3 ^(IV). To achieve a bracing effect in the axial direction of carrier pipe 3 ^(IV), it may be advantageous to provide a temperature difference between the pin 4 and the other elements, in particular the carrier pipe 3 ^(IV), in assembly of the pin 4.

FIG. 6

In this embodiment, the carrier pipe 3 ^(V) is part of one of two individual cams 1, 2. Fastening of the individual cam 1 and/or 2, which is not a fixed part, on this carrier pipe 3 ^(V) is accomplished in the manner already described in conjunction with the other exemplary embodiments.

FIG. 7

This embodiment of a multiple cam that has been assembled and joined differs from that in FIG. 5 only in that the carrier pipe 3 ^(IV) here is joined to the individual cams 1, 2 and is designed at both ends in the manner of the embodiment according to FIG. 5 with the help of pin 4.

FIG. 8

In this embodiment a part of a carrier pipe 3 ^(VII) is integrally molded on each of the two individual cams 1, 2. The integrally molded parts of the carrier pipe 3 ^(VII) are designed so that they can be telescoped one into the other. In the required pinning to an internal shaft of an adjustable camshaft, the pin 4 may be passed through the telescoping individual areas of the carrier pipe 3 ^(VII). After the pinning has been accomplished, the individual cams 1, 2 are exclusively aligned and secured with respect to one another by this pinning. The two individual areas of the carrier pipe 3 ^(VII) emanating from the individual cams 1, 2 may also be joined together according to one of the options given above for the other types of connection, i.e., in particular they may be joined together by welding, soldering and/or gluing.

FIG. 9

This embodiment variant corresponds to that according to FIG. 2 with the difference being only that the carrier pipe 3 ^(VIII) protrudes axially beyond the individual cams 1, 2 at its ends.

FIG. 10

In this embodiment, the carrier pipe 3 ^(IX) is a fixed part of the individual cams 1, 2. This multiple cam may be originally shaped in this form, reshaped or manufactured by machining. The radial inside circumference of the carrier 3 ^(IX) has a slightly enlarged inside diameter in comparison with the adjacent individual cams 1, 2. This area having an enlarged inside diameter offers the advantages already discussed in conjunction with a carrier pipe 3 having a similarly enlarged inside circumference in the embodiment according to FIG. 3.

All the features described in the description and characterized in the following claims may be essential to the invention either when used individually or combined together in any form. 

1. A joined prefabricated individual cam comprising multiple cams for an adjustable camshaft in particular for an internal combustion engine of a motor vehicle, whereby the camshaft has two shafts mounted concentrically one inside the other, namely an inner shaft and an outer shaft, and the joined multiple cam is fixedly pinned to the inner shaft through radial openings provided in the outer shaft with a rotatable bearing on the outer shaft, wherein at least one prefabricated individual cam (1, 2) is placed as a cam ring on the outside circumference of a carrier pipe (3) at an axial distance from a neighboring individual cam (1, 2) and is fixedly connected to this carrier pipe (3) in a predetermined angle of rotation and axial distance assignment.
 2. The joined multiple cam according to claim 1, wherein the at least one individual cam (1, 2) is placed on a circular cylindrical circumferential area of the carrier pipe (3).
 3. The joined multiple cam according to claim 1, wherein the carrier pipe (3) is designed and manufactured in one piece with the individual cam (1, 2).
 4. The joined multiple cam according to claim 1, wherein an axial distance between two individual cams (1, 2) is defined by a ring collar (5) provided axially on the carrier pipe (3).
 5. The joined multiple cam for an adjustable camshaft according to claim 1, wherein the carrier pipe (3) has at least one radial opening for pinning the multiple cam to an inner shaft of the adjustable camshaft, said radial opening being situated outside of the circumferential areas taken up by the individual cams (1, 2).
 6. The joined multiple cam according to claim 1, wherein the axial distances between the individual cams (1, 2) are maintained by spacer rings (8) placed on the carrier pipe.
 7. The joined multiple cam according to claim 1, wherein pins (4) that can be inserted into the carrier pipe (3) to pin it to the inner shaft of an adjustable camshaft exert axial and/or rotational angle fixation functions simultaneously for at least one of the individual cams (1, 2) in the inserted state.
 8. The joined multiple cam according to claim 1, wherein the ring collar (5) of the carrier pipe (3) is an area created on the carrier pipe (3) by an internal high-pressure shaping process.
 9. The joined multiple cam according to claim 1, wherein the carrier pipe (3) has a larger inside diameter in comparison with axially neighboring areas in its at least one pinned area.
 10. The joined multiple cam according to claim 1, wherein two neighboring individual cams (1, 2) each have an integrally molded partial piece of the carrier pipe (3), whereby these partial pieces are telescoped into one another when the individual cams (1, 2) are joined.
 11. The joined multiple cam according to claim 1, wherein at least one part of the individual elements is joined together by at least one or a combination of several of the following types of joining, namely a press fit, a weld, a glued joint, a soldered joint or a form-fitting connection. 